Extraction of chlorophylls and carotenoids from dry and wet biomass of isolated Chlorella Thermophila: Optimization of process parameters and modelling by artificial neural network

Chlorophylls and carotenoids can be extracted from microalgae using various solvents. However, there is lack of studies regarding the comparison of extraction yield of these pigments from wet and dry microalgal biomass using different combination of cell disruption methods. Therefore, in this work, we have investigated the comparison of the extraction yield of chlorophylls and carotenoids from the wet and heat-dried microalgal biomass (isolated Chlorella thermophila) using ethanol. Extraction parameters such as homogenisation time, homogenisation speed, solvent temperature, solid-solvent ratio, boiling time and microwave time have been optimised. Chlorophyll extraction yield was observed to be 2.7 fold higher from wet biomass than dry biomass while carotenoid yield was 6.7 fold higher. Highest chlorophyll yield (～60 mg/g-dry biomass) was observed at 6 min of homogenisation time, 10,000 rpm, solid solvent ratio of 1 mg/mL and 58 °C of solvent temperature from wet biomass with extraction efficiency of ～94 %. Highest carotenoid yield was noticed following the same conditions of chlorophyll extraction except 4 °C of solvent temperature. The modelling of the extraction process was performed using artificial neural network (ANN) which may be useful for the scale-up of the extraction process at the industrial level.